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Help with a number sequence! Year 4, but really hard [blush]

(7 Posts)
Sticklebug Tue 07-May-13 20:43:50

My year 4 DD has been asked to complete the following number sequence.

7, 19, 55

She has no idea, my older DD has no idea and I have absolutely no idea.....Any help???

AnythingNotEverything Tue 07-May-13 20:50:08

Is it times by 3 and minus 2?

SconeInSixtySeconds Tue 07-May-13 20:51:25

7x3 = 21
21-2 = 19

19x3=57
57-2=55

It's a two step pattern..evil but fun to us mad maths sickos

Sticklebug Tue 07-May-13 20:51:59

My DD(11) has just rushed down stairs saying the same thing....I just could not see it!

Sticklebug Tue 07-May-13 20:52:25

Is this hard for yr4...or maybe I am not as good at maths as i thought!

richmal Wed 08-May-13 11:08:50

There are some good expanations for the sequence 3, 7, 19, 55 on nrich.

mccandjt Mon 20-May-13 14:38:02

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